In forage harvesters of the above type, control of the spout position and of the position of a pivotable end portion (flap) of the spout on the basis of camera images is known in the art. Patent publication WO-A-2011/101458 describes a system in which a 3D camera is arranged on the discharge spout. The camera takes images of the container driving next to the machine. These images define at least two vertical strips. Analysis of these strips provides the position of the front and/or rear wall of the container relative to the camera. Based on this information, the spout is controlled so that the crop material is unloaded in the container.
Patent publication WO-A-2013/120079 A1 shows a system using the images from two cameras to align the spout with a target zone of the container. This may be achieved by repositioning the spout and or changing the speed of the harvester. These prior art systems react to changes in the actual images and may not always have sufficient time for realigning the spout when one or more harvesting or field conditions suddenly change, such that some crop may be lost.